I've been keeping a close eye on the N55 turbo developments for a year now, and Vargas finally has a turbo bolted onto a test car.
http://www.e90post.com/forums/showthread.php?t=905962
I have to say, I am seriously considering it. I want to wait and see what the dyno numbers and tuning support are like before committing for that kind of cash, but if it really does put out over 500 whp like they think it will, I will likely bite. I like the fact it is a hybrid solution that appears stock and is compatible with the aftermarket parts I already have.
I just think the prospect of a 500 wheel horsepower X1 is ridiculously awesome. Car would low-mid 11s 1/4 mile with 500whp.